1. a+b+c=630
b=4a=2c
4(a+b+c)=4*630
4a+4b+4c=2520
b+4b+2b=2520
7b=2520 :7
b=360
a=360:4=90
c=360:2=180
Verificare: 90+360+180=630
2. a+b+c=369
a=[tex] \frac{3}{4} [/tex]b
b=2c
[tex] \frac{3}{4} [/tex]b+b+[tex] \frac{1}{2} [/tex]b=369
3b+4b+2b=4*369
9b=1476 :9
b=164
a=[tex] \frac{3}{4} [/tex]164=123
c=82
Verificare: 123+164+82=369
3. Notam: a=gaini, b=gaste, c=oi
a+b+c=71 in functie de numarul de capete
2a+2b+4c=172 in functie de numarul de picioare
b=[tex] \frac{1}{3} [/tex]a => a=3b
4b+c=71 => c=71-4b
8b+4c=172
8b+4(71-4b)=172
-8b=172-284
8b=112 :8
b=14 gaste
a=3*14=42 gaini
c=71-42-14=15 oi
Verificare: 2*42+2*14+4*15=84+28+60=172
